1. Field of the Invention
This invention relates generally to apparatus for generating an audible signal and relates particularly to a portable underwater signalling transducer in which a diver equipped with scuba gear may produce a high powered signal to call for help, warn other divers, help locate the position of other divers under difficult conditions, or communicate with surface or underwater vessels through a prearranged code.
2. Description of the Prior Art
Heretofore many sound generating devices have been provided for shipboard use to produce a high powered sound under water for either seismic or communication purposes. Most of the prior art devices have utilized steam, electrodynamic or hydrodynamic components to generate acoustic waves which pass through the water. Most of these prior art devices have been large and bulky and accordingly have not been acceptable for divers using scuba gear. Some examples of this type of prior art are the patents to Mellen U.S. Pat. Nos. 3,246,289, Sharp et al 3,433,202 and Copley 3,560,913.
Alsp some signalling devices have been provided for divers using scuba gear, such as the patents to Gagnan et al U.S. Pat. Nos. 3,144,171 and Christianson 3,719,160 which are connected to the scuba gear of a diver to produce an audible sound when the pressure in the air tanks has dropped to a predetermined low pressure. However, the structure defined by these patents is adapted to operate automatically when the pressure decreases and cannot be selectively operated by the diver.